Not OP, but if I was to do this, I'd start by downloading Wikipedia and all its external links and references, and crawling from there. You should eventually reach most of the publicly visible internet.
When I did some crawler experimenting in my younger years, I thought I was pretty clever using sites that would let you perform a random Google searches. I would just crawl all the pages from the results returned.
Your method would undoubtedly be more interesting I think. It would certainly lead to interesting performance problems quicker, I bet.